CARBURETOR CIRCUITS AND COMPONENTS CBC AUTOMOTIVE TECHNOLOGY

BASIC CARB DESIGN Conventional Design Computer Control for Better Fuel Metering 1,2,3,4 barrel carbs

CARBURETOR SYSTEMS FLOAT SYSTEMS Pg 7 Float Material Maintains Level Float setting Viton Needle and Seat Dampening Spring Float Bowl Construction Float Drop

FLOAT BOWL VENT Vented to outside atmosphere Vapor Seperator Mechanical Vent Dirty air filters affect pressure in bowl Usually located near center of bowl

IDLE SYSTEM Not enough airflow at idle to allow main system to operate Pg 8 IDLE SYSTEM Not enough airflow at idle to allow main system to operate Manifold vacuum is high to draw fuel out idle ports Usually adjustable Idle air bleed helps atomize fuel and prevents siphoning

TRANSFER CIRCUIT Transfers fuel off in Off idle mode Pg 8 TRANSFER CIRCUIT Transfers fuel off in Off idle mode Adds fuel to mixture as throttle plate opens to cover “sag”

MAIN SYSTEM Fuel supplied by “main jets” Operates under high venturi vacuum Atmospheric Pressure pushes fuel out discharge nozzel

ACCELERATOR PUMP SYSTEM

HOT IDLE COMPENSATOR Allows mixture to be lean out during hot idle conditions caused by excessive fuel vapor

CHOKE TYPES Automatic Chokes Integeral Choke Divorced Choke Manual Hot Air Electric Integeral Choke Divorced Choke

CHOKE SYSTEM Operates when cold and low rpm Pg 10 CHOKE SYSTEM Operates when cold and low rpm Sometimes fuel extracted from air bleed holes Allows 5:1 mixture Vacuum Break or Choke Pull Off

CHOKE SYSTEM

CHOKE COIL OPERATION

CHOKE PULLOFF Forces the choke open slightly just after engine starts. Position determined by torque of coil air velocity on blade vacuum on piston must adjust correctly!

POWER CIRCUITS Mechanical Power Valve Adjustable Sometimes combination with metering rods Flows through a circuit into main metering system

VACUUM POWER VALVE Different locations on carbs. Usually in bowl area. Pg 8 VACUUM POWER VALVE Different locations on carbs. Usually in bowl area. Supplies Extra fuel under heavy loads Operated by Manifold Vacuum

BAROMETRIC PRESSURE COMPENSATOR Compensates for altitude Fairly troublefree

THROTTLE POSITION SENSOR

IDLE SPEED CONTROL

A/C IDLE SOLENOID Used with A/C Compensates for drag on engine caused by Compressor Adjustment is usually seperate from Curb Idle rpm.

TYPES OF CARBURETORS

TERMINOLOGY Emulsion Float Circuit Lean Metering Metering Rod Power Valve Rich Stoichiometric ratio Throttle Kicker Throttle stop solenoid Transfer slot Vaporization variable venturi Venturi Air Bleed